1. Field of the Invention
The present invention relates to a microfluidic device for electrically regulating the pH of a fluid therein and a method of regulating the pH of a fluid in a microfluidic device using the same.
2. Description of the Related Art
Microfluidic devices are devices in which an inlet, an outlet, a reaction chamber, etc., are interconnected through microchannels. Such devices are widely known in the field and are used in micro-analytic devices, such as a lab-on-a-chip (LOC). In addition to microchannels, a micropump for inducing the flow of fluid, a micromixer for mixing fluids, a microfilter for filtering a fluid, etc., may be included in microfluidic devices.
A microfluidic device used as a biological analytic device, such as a LOC, performs a series of biological analytic processes including cytolysis, nucleic acid amplification and separation, for example, a polymerase chain reaction (PCR), and protein separation and detection. A conventional pH regulating process involved in such biological analysis processes includes adding or removing an acidic solution, a neutral solution, or a buffer solution. However, when adding or removing a pH-adjusting solution in a microfluidic device, problems associated with dilution, mixing and the flow of a substance in a microchannel may arise because a small amount of a sample is used. Furthermore, the added pH-adjusting material may inhibit subsequent biological analysis processes. In this case, the pH-adjusting material has to be removed.
A method of adjusting the pH using electrolysis can be considered as a solution to the above conventional problems associated with the injecting pH-adjusting reagent. In the method, a microfluidic device includes an electrode and a chamber in which water can be electrolyzed. When a voltage is applied to the chamber, water is electrolyzed. Accordingly, the pH can be regulated by hydrogen ions generated by the anode and hydroxide ions generated by the cathode. However, when negatively charged biological molecules such as nucleic acids are absorbed into the positive electrode, the absorbed molecules generally become unstable and the efficiency of the process can deteriorate. The inventors of the present invention found a method of regulating the pH in a microfluidic device using electrolysis of water and preventing materials such as nucleic acids from being absorbed into the positive electrode to which a voltage is applied, and thus increasing the efficiency of the process by increasing the stability of the nucleic acids, etc.